Rhamnolipids have been found to have antimicrobial properties. They can inhibit microbial growth and damage or kill microbial cells at concentrations above certain critical levels. Because of this antimicrobial activity, rhamnolipids have been reported for potential use as a biopesticide.
Rhamnolipids also have surfactant properties. Based on the surfactant properties, rhamnolipid solutions first act to detach and remove particles (including living organisms, spores, “eggs” of pests) from surfaces of plants. However, microorganisms typically have cell walls to protect them from various harmful factors, including biosurfactants, they may experience in their living environments. While rhamnolipids are effective against many of these walled microbial cells, the concentrations required can be high and the effects may be more of the inhibitory nature, rather than a lethal impact. The use of rhamnolipids at these high concentrations not only makes it costly, but also less selective towards the target pests. That is, at these higher concentrations, rhamnolipids can be inhibitory to multitudes of unintended organisms and actually become ecological stressors to the applied area.
Rhamnolipids also are biodegradable. While this property makes them more environmentally friendly for agricultural uses, it also forces frequent applications to the plants. Requiring frequent applications significantly increases the material, operating, and labor costs for use of rhamnolipids as biopesticides.
It is also taught in the art to prepare calcium rhamnolipid complexes. For example, U.S. Pat. No. 9,468,700 discloses the use of calcium rhamnolipid complexes that are designed to be effective when provided in a wound dressing.